Transmission protection

ABSTRACT

Communication between a cellular network and a communication device occurs in a first frequency band and a second frequency band, the second frequency band being at least partly different from the first frequency band. A data packet is sent in the first frequency band. Depending on an acknowledgment of receipt of the data packet, the data packet is selectively sent in the second frequency band.

FIELD OF THE INVENTION

Various embodiments relate to a communication device, to a node of acellular network, and to corresponding methods. In particular, variousembodiments relate to techniques of protecting uplink transmissionand/or downlink transmission between the communication device and thecellular network.

BACKGROUND OF THE INVENTION

With increasing popularity of mobile voice and data communication, thereis an ever increasing demand for high-speed voice and datacommunication. The licensed spectrum for cellular communication israpidly being exhausted by a dense and growing subscriber base. Thisapplies in particular to the valuable low-frequency bands with lowpropagation loss traits.

A significant amount of unlicensed spectrum or unlicensed bands isavailable. For illustration, a significant amount of spectrum isglobally available in the 5 GHz frequency band. Within the Long TermEvolution (LTE) radio access technology as specified by the ThirdGeneration Partnership Project (3GPP), it is desirable to employ theunlicensed bands. It is desirable to utilize the License AssistedAccess—LTE (LAA-LTE) procedure to augment the capacity of licensedfrequency bands in the unlicensed bands. LAA-LTE may be used forcarrying data traffic for mobile services. The purpose of LAA-LTE is toextend LTE cellular communication to the unlicensed spectrum. Sometimes,LAA-LTE is also referred to as LTE-unlicensed (LTE-U).

In the licensed frequency bands, there is typically operator controlover resource management both in frequency and time domain. This isreferred to operator-controlled network deployment. Further,transmission may be protected by employing Automatic Repeat Request(ARQ) schemes. Typically, the resource management and/or the ARQ schemeis implemented to a significant degree in the Data Link Layer comprisingthe Medium Access (MAC) layer, according to the Open SystemInnterconnection (OSI) Model standardized by the InternationalTelecommunication Union (ITU).

Employing LAA-LTE or transmission of data packets typically facesrestrictions in terms of transmission reliability. Protection ofsuccessful transmission may be possible to a limited degree only. E.g.,if compared to the licensed spectrum, the ARQ process can be lesspredictable, as the medium is shared in a more or less uncontrolledmanner between different parties. E.g., the transmission channel in theunlicensed band could be used by third parties. E.g., the unlicensedband could be used by other network providers, private persons and otherbusiness segments. Third parties could employ LTE, Wireless Local AreaNetwork (WiFi), radar and/or other communication problems. The so-calledhidden node problem may occur where the transmitting device may not beable to detect interfering radio signals.

BRIEF SUMMARY OF THE INVENTION

Therefore, a need exists to provide advanced techniques of protectinguplink transmission and/or downlink transmission between a communicationdevice and a cellular network. In particular, a need exists for suchtechniques which employ the opportunities offered by the unlicensedspectrum and/or LAA-LTE while, at the same time, a reliable uplinktransmission and/or downlink transmission is ensured.

This need is met by the features of the independent claims. Thedependent claims define embodiments.

According to an aspect, a communication device is provided. Thecommunication device comprises a wireless interface. The wirelessinterface is configured to communicate with a cellular network in afirst frequency band. The wireless interface is further configured tocommunicate with a cellular network in a second frequency band. Thesecond frequency band is at least partly different from the firstfrequency band. The communication device further comprises at least oneprocessor. The at least one processor is configured to send a datapacket to the cellular network via the wireless interface in the firstfrequency band. The at least one processor is further configured tocheck if receipt of the data packet is acknowledged by the cellularnetwork. The at least one processor is further configured to selectivelysend a data packet to the cellular network via the wireless interface inthe second frequency band, depending on said checking.

According to an aspect, a method is provided. The method comprises atleast one processor of a communication device sending a data packet tothe cellular network via wireless interface of the communication devicein a first frequency band. The method further comprises the at least oneprocessor checking if receipt of the data packet is acknowledged by thecellular network. The method further comprises, depending on saidchecking, the at least one processor selectively sending the data packetto the cellular network via the wireless interface in a second frequencyband. The second frequency band is at least partly different from thefirst frequency band.

According to an aspect, a node of a cellular network is provided. Thenode comprises a wireless interface. The wireless interface isconfigured to communicate with a communication device connected to thecellular network in a first frequency band. The wireless interface isfurther configured to communicate with the communication device in asecond frequency band. The second frequency band is at least partlydifferent from the first frequency band. The node further comprises atleast one processor. The at least one processor is configured to send adata packet to the communication device via the wireless interface inthe first frequency band. The at least one processor is furtherconfigured to check if receipt of the data packet is acknowledged by thecommunication device. The at least one processor is further configuredto selectively send the data packet to the communication device via thewireless interface in the second frequency band depending on saidchecking.

According to an aspect, a method is provided. The method comprises atleast one processor of a node of a cellular network sending a datapacket to a communication device connected to the cellular network viawireless interface of the node in the first frequency band. The methodfurther comprises the at least one processor checking if receipt of thedata packet is acknowledged by the communication device. The methodfurther comprises, depending on said checking the at least one processorselectively sending the data packet to the communication device via thewireless interface in a second frequency band. The second frequency bandis at least partly different from the first frequency band.

According to a further aspect, a node of a cellular network is provided.The node comprises a wireless interface. The wireless interface isconfigured to communicate with the communication device connected to thecellular network in a first frequency band. The wireless interface isfurther configured to communicate with the communication device in asecond frequency band. The second frequency band is at lest partlydifferent from the first frequency band. A node further comprises atleast one processor configured to receive a data packet from thecommunication device via the wireless interface in the first frequencyband. The at least one processor is further configured to check ifreceipt of the data packet is successful. The at least one processor isfurther configured to selectively receive the data packet from thecommunication device via the wireless interface in the second frequencyband, depending on said checking.

According to a further aspect, a method is provided. The methodcomprises at least one processor of a node of a cellular network,receiving a data packet from a communication device via wirelessinterface of the node in a first frequency band. The method furthercomprises the at least one processor checking if receipt of the datapacket is successful. The method further comprises the at least oneprocessor selectively receiving the data packet from the communicationdevice via the wireless interface in a second frequency band, dependingon said checking. The second frequency band is at least partly differentfrom the first frequency band.

According to an aspect, a communication device is provided. Thecommunication device comprises a wireless interface which is configuredto communicate with the cellular network in a first frequency band andto communicate with the cellular network in a second frequency band. Thesecond frequency band is at least partly different from the firstfrequency band. The communication device further comprises at least oneprocessor. The at least one processor is configured to receive a datapacket from the cellular network via the wireless interface in the firstfrequency band. The at least one processor is further configured tocheck if receipt of the data packet is successful. The at least oneprocessor is further configured to selectively receive the data packetfrom the cellular network via the wireless interface in the secondfrequency band, depending on said checking.

According to an aspect, a method is provided. The method comprises atleast one processor of a communication device connected to a cellularnetwork receiving a data packet from the cellular network via a wirelessinterface of the communication device in a first frequency band. Themethod further comprises the at least one processor checking if receiptof the data packet is successful. The method further comprises the atleast one processor selectively receiving the data packet from thecellular network via the wireless interface in a second frequency band,depending on said checking. The second frequency band is at least partlydifferent from the first frequency band.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will be described with reference to theaccompanying drawings in which the same or similar reference numeralsdesignate the same or similar elements.

FIG. 1 is a schematic representation of a communication device connectedto a cellular network communicating with the cellular network via afirst frequency band and via a second frequency band according tovarious embodiments.

FIG. 2 is a signalling diagram illustrating protection of uplinktransmission of a data packet from the communication device to thecellular network according to various embodiments.

FIG. 3 is a signalling diagram illustrating protection of downlinktransmission of a data packet from the cellular network to thecommunication device according to various embodiments.

FIG. 4 is a signalling diagram illustrating protection of uplinktransmission of a data packet from the communication device to thecellular network according to various embodiments.

FIG. 5 is a schematic illustration of a first ARQ scheme and a secondARQ scheme for protection of transmission of the data packet accordingto various embodiments.

FIG. 6 is a schematic illustration of the data packet according tovarious embodiments.

FIG. 7 is a schematic illustration of the communication device atgreater detail according to various embodiments.

FIG. 8 is a schematic illustration of a node of the cellular networkaccording to various embodiments.

DESCRIPTION OF EMBODIMENTS

Exemplary embodiments of the invention will be described with referenceto the drawings. While some embodiments will be described in the contextof specific fields of application, e.g. in the context of certainspectral ranges and communication techniques, the embodiments are notlimited to this field of application. The features of the variousembodiments may be combined with each other unless specifically statedotherwise.

The drawings are to be regarded as being schematic representations andelements illustrated in the drawings are not necessarily shown to scale.Rather, the various elements are represented such that their functionand general purpose become apparent to a person skilled in the art. Anyconnection or coupling between functional blocks, devices, components,or other physical or functional units shown in the drawings or describedherein may also be implemented by an indirect connection or coupling. Acoupling between components may also be established over a wirelessconnection. Functional blocks may be implemented in hardware, firmware,software, or a combination thereof.

Hereinafter, techniques of protecting uplink transmission of a datapacket from a communication device to a cellular network are described.Furthermore, techniques of protecting downlink transmission of a datapacket from the cellular network to the communication device aredescribed. Both techniques relate to, first, transmitting the datapacket via a first frequency band; depending on whether receipt of thedata packet is successful, the data packet is selectively transmittedvia a second frequency band. In this regard, it is possible to check ifreceipt of the data packet has been acknowledged, e.g., not acknowledgednegatively and/or positively acknowledged, etc.

Hereinafter, for illustrative purposes reference will be primarily madeto the transmission of the data packet relying on 3GPP LTE radio accesstechnology. In particular, reference will be made to the first frequencyband being an unlicensed frequency band and the transceiving of datapackets via the unlicensed frequency band being according to the LAA-LTEtransmission procedure; for sake of simplicity, the first frequency bandwill therefore be referred to as the LAA-LTE frequency band. Likewise,reference will be primarily made to the second frequency band being alicensed frequency band and the transceiving of data packets via thelicensed frequency band (LTE frequency band) being according to theconventional licensed LTE data transmission procedure. Yet, it should beunderstood that such techniques may be readily applied to differentkinds of frequency bands and different kinds of radio access technology.E.g., a scenario is possible where communication via the first frequencyband is according to the 3GPP Universal Mobile Telecommunications System(UMTS) radio access technology, while communication via the secondfrequency band is according to the 3GPP LTE radio access technology. itis possible that transmitting the data packet in the first frequencyband employs a listen-before-talk traffic control technique.Transmitting the data packet in the second frequency band may employ acentral resource scheduling scheme as a traffic control technique.Hence, collision avoidance techniques may be according to a bottom-upapproach in the first frequency band and according to a top-downapproach in the second frequency band.

In FIG. 1, the communication between the communication device (UE) 101and the cellular network 102 (labelled NET in FIG. 1) is shown. As canbe seen from FIG. 1, there are two communication channels available forthe communication. A first communication channel employs the firstfrequency band 111; a second communication channel employs the secondfrequency band 112. In the scenario of FIG. 1, the communication isaccording to the 3GPP LTE access technology. Communication via the firstLAA-LTE frequency band 111 employs the 3GPP LAA-LTE radio accesstechnology; communication via the second LTE frequency band 112 employsthe conventional 3GPP LTE radio access technology. The transmission inFIG. 1 is bi-directionally between the UE 101 and the cellular network102: uplink transmission 181 is possible from the UE 101 to the cellularnetwork 102; downlink transmission 182 is possible from the cellularnetwork 102 to the UE 101.

Generally, the type and kind of the UE 101 is not particularly limited.E.g., the UE 101 may be one of a mobile phone, a smartphone, tablet, apersonal digital assistant, a mobile music player, a smart watch, awearable electronic equipment, and a mobile computer.

In the scenario of FIG. 1, the cellular network 102 comprises two accessnodes in the form of evolved Node Bs (eNBs) 102 b, 102 c forcommunication via the LAA-LTE frequency band 111 and the LTE frequencyband 112, respectively. Because there are two access nodes employed,this scenario is sometimes referred to as dual connectivity. It is alsopossible that one and the same access node supports communication viathe LAA-LTE frequency band 111 and the LTE frequency band 112; as insuch a scenario there is a single access node employed, this scenario issometimes referred to as co-located. If two access nodes are employed,the two access nodes may be co-located. The eNBs 102 b, 102 b areconnected to the core network 102 a of the cellular network 102.

In FIG. 1, a scenario is illustrated where transmission 181, 182 betweenthe UE 101 and the cellular network 102 relies on the two frequencybands 111, 112. Generally, it is possible that the transmission 181, 182between the UE 101 and the cellular network 102 relies on a largernumber of frequency bands (not shown in FIG. 1). E.g., it is possiblethat there is more than one unlicensed frequency band available for thetransmission 181, 182. Then, it is possible that the transmission 182,182 is distributed between the licensed frequency band 112 and allavailable unlicensed frequency bands.

Further, in FIG. 1, a scenario is shown, where the LAA-LTE frequencyband 112 is different from the LTE frequency band 111, i.e., notoverlapping in frequency space. Generally, it is possible that thefrequency bands 111, 112 are at least partly different from each other;e.g., it is possible that the frequency bands 111, 112 are at leastpartly overlapping in frequency space.

Hereinafter, techniques are described which enable to protect thetransmission 181, 182 of one or more data packets between the UE 101 andthe cellular network 102. This protection employs a fallback scenario:If the transmission 181, 182 via the LAA-LTE frequency band 111 isunsuccessful or fails, transmission 181, 182 via the LTE frequency band112 is used as a fallback. According to the techniques describedhereinafter, this fallback is configurable; i.e., a trigger criterionwhich triggers the fallback may be flexibly set and/or negotiatedbetween the cellular network 102 and the UE 101.

E.g. one trigger criterion for the fallback to transmission 181, 182 viathe LTE frequency band 112 may be acknowledgement of the transmission181, 182 of the one or more data packets via the LAA-LTE frequency band111. E.g., in a scenario where the uplink transmission 181 from the UE101 of the cellular network 102 is protected, it is possible that thereceiving entity 101, 102 checks if the one or more data packets havebeen successfully received; this may be achieved by employing areception window technique and/or acknowledgement requests. Depending onsaid checking, it is possible that the receiving entity 101, 102positively acknowledges and/or negatively acknowledges the transmission181, 182 of the one or more data packets. This may be done by means of adedicated acknowledgement message. Block acknowledgement and/or implicitacknowledgement may be relied upon. Then, the sending entity 101, 102may check the acknowledgement status and use this acknowledgement statusas the decision criterion for triggering the fallback.

Examples are given hereinafter. E.g., for protection of uplinktransmission 181, it is possible that the UE 101 checks if receipt ofthe one or more data packets is acknowledged by the cellular network102. Then, depending on said checking, it is possible that the UE 101 isconfigured to selectively send the one or more data packets to thecellular network 102 in the LTE frequency band 102. Likewise, in thescenario where downlink transmission 182 from the cellular network 102to the UE 101 is protected, it is possible that the eNB 102 c checks ifreceipt of the one or more data packets is acknowledged by the UE 101;then, the eNB 102 b can be configured to selectively send the one ormore data packets to the UE 101 in the LTE frequency band 112 dependingon said checking.

E.g., in the scenarios of uplink transmission 181 and downlinktransmission 182 as mentioned above, it is possible that positiveacknowledgement and/or negative acknowledgement of the transmission 181,182 of the one or more data packets is monitored. E.g., if thesuccessful transmission 181, 182 of the one or more data packets betweenthe UE 101 and the cellular network 102 is not positively acknowledged,it is possible that the fallback to the LTE frequency band 112 istriggered. Likewise, it is possible that if only negativeacknowledgements or no acknowledgements at all are received for thetransmission 181, 182 of the one or more data packets between the UE 101and the cellular network 102, the fallback to the transmission via theLTE frequency band 112 is triggered. As can be see from the above,various trigger criteria for triggering the fallback of transmission181, 182 via the LTE frequency band 112 are conceivable. Generally, suchdecision criteria can be combined in various manners according tovarious embodiments.

Employing such techniques as explained allows achieving various effects.E.g., it is possible that a comparably high transmission reliability isachieved. This may be the case because transmission 181, 182 is firstattempted via the LAA-LTE frequency band 111 and then, additionally,attempted via the LTE frequency band 112. In particular, thetransmission 181, 182 via the LTE frequency band 112 may be comparablyfail-safe and reliable. Transmission protection may be possible in theLAA-LTE frequency band 111 and/or the LTE frequency band 112 based onvarious protection techniques such as a Hybrid ARQ (HARQ) scheme andForward Error Correction (FEC). E.g., if the protected transmission thatemploys the LAA-LTE protocol in the LAA-LTE frequency band 111 fails,then the remaining HARQ procedure can be executed in the LTE frequencyband 112. As a further effect, it may be possible to reduce thesignalling load imposed on the LTE frequency band 112; this is because afirst try of transmission 181, 182 is executed in the LAA-LTE frequencyband 111.

Generally, it is possible that the transmission 181, 182 of the one ormore data packets via the LAA-LTE frequency band 111 is protected usinga first HARQ scheme; likewise, the transmission 181, 182 via the LTEfrequency band 112 can be protected using a second ARQ scheme. Here, thefirst and second HARQ schemes may differ with respect to one or morecorresponding configuration parameters such as a transmission retrycounter, a transmission timeout timer, a transmission retry timer, blockacknowledgement, and/or immediate acknowledgement, etc. By suchtechniques, an better balance between reliability of transmission of thedata packet one the one hand and load balancing between the LAA-LTEfrequency band 111 and the LTE frequency band 112 may be achieved.

Turning to FIG. 2, a signaling diagram for communication between the UE101 and the eNBs 102 b, 102 c is illustrated for scenarios where theuplink transmission 181 of a data packet 290 is protected.

In FIG. 2, the UE 101 has a memory (not shown in FIG. 2) which iscontrolled to implement a transmission buffer. E.g., the transmissionbuffer may reside in the MAC layer according to the ITU OSI model. At201, the data packet 290 is received from a higher layer and written tothe transmission buffer.

Execution of 201 triggers initialization of a transmission timeout timer280-1. E.g., the transmission timeout timer 280-1 may be initializedwhen the packet 290 is received from the higher layer or when the packetis written to the transmission buffer or some time later.

At 202, the data packet 290 is sent via the LAA-LTE frequency band 111to the eNB 102 c. The eNB 102 c checks if receipt of the data packet 290is successful. Checksums may be employed. Forward Error Correction (FEC)may be employed.

Yet, in the scenario of FIG. 2, the data packet 290 cannot be receivedsuccessfully at least in parts. Thus, the transmission is unsuccessful.I.e., parts or all of the data packet 290 may be lost; it may not bepossible or only possible with comparably low reliability tore-construct missing parts of the data packet 290 employing, e.g., FEC.

Because the transmission is unsuccessful at 202, a negativeacknowledgement 203 is sent from the eNB 102 c to the UE 101. In casethe transmission of the data packet 290 should have been successful (notshown in FIG. 2), a positive acknowledgement would have been sent fromthe eNB 102 c to the UE 101 (not shown in FIG. 2).

The transmission of the negative acknowledgement 203 successful, i.e.,the UE 101 receives the negative acknowledgement 203 which, in turn,indicates that the transmission of the data packet 290 at 202 was notsuccessful. At this point, the transmission timeout timer 280-1 has notexpired yet.

Because of this, the UE 101 retries transmission of the data packet 290at 204. Again, the uplink transmission 181 of the data packet 290 isunsuccessful at 204 which triggers the negative acknowledgment 205.Then, the UE 101 again re-sends the data packet 290 at 206; again, theuplink transmission 181 is unsuccessful which triggers the sending ofthe negative acknowledgement 207. As can be seen, the transmission 181of the data packet 290 at 202, 204, 206 occurs as part of a first ARQscheme which tries to successfully transmit the data packet 290 via theLAA-LTE frequency band 111.

Then, the retransmission timeout timer 280-1 expires. This is thetrigger criterion for executing the fallback to uplink transmission 181of the data packet 290 via the LTE frequency band 112, i.e., to the eNB102 b. At 208, this uplink transmission 181 of the data packet 290 viathe LTE frequency band 112 commences. Also the uplink transmission 181of the data packet 290 at 208 is unsuccessful; this triggers the sendingof the negative acknowledgement 209 from the eNB 102 b to the UE 101 viathe LTE frequency band 111. The UE 101 receives the negativeacknowledgement 209 which triggers re-sending of the data packet 290 at210. Finally, the transmission 210 of the data packet 290 is successful,i.e., the eNB 102 b successfully receives the data packet 290 withouterrors. This successful receiving of the data packet 290 at 210 ispositively acknowledged at 211.

From FIG. 2, it can be seen that the uplink transmission 181 via the LTEfrequency band 112 is accompanied by monitoring transmission timeoutemploying a further transmission timeout timer 280-2. The furthertransmission timeout timer 280-2 does not expire before receipt of thedata packet 290 is positively acknowledged at 211 by the cellularnetwork 102. However, if the further transmission timeout timer 280-2would have expired before the packet 290 is positively acknowledged (notshown in FIG. 2), the nodes 102 b, 102 c are allowed to delete allbuffered data relating to that packet 290 from their receive buffers(not shown in FIG. 2). Potential further retransmission are handled bylayers higher than the MAC layer, e.g., according to the TransmissionControl Protocol (TCP).

As will be appreciated from the above, the transmission timeout of theuplink transmission 181 of the data packet 290 via the LAA-LTE frequencyband 111 is monitored. When the transmission timeout timer 280-1 has notyet expired, checking if receipt of the data packet 290 is acknowledgedby the cellular network 102 yields that the receipt of the data packet290 is not positively acknowledged, i.e., no positive acknowledgementhas been received, but only the negative acknowledgements 203, 205, 207are received. This trigger re-sending the data packet 290 via theLAA-LTE frequency band 111 at 204, 206. When the transmission timeouttimer 280-1 has expired, checking if receipt of the data packet 290 isacknowledged by the cellular network 102 yields again that the receiptof the data packet 290 is not positively acknowledged. This triggers theuplink transmission 181 via the LAA-LTE frequency band 112. I.e., if themonitoring of the transmission timeout yields an elapsed transmissiontimeout timer 280-1 of the data packet 290, sending of the data packet290 to the cellular network 102 in the LTE frequency band 112 isexecuted. By such techniques, it can be ensured that the communicationsystem comprising the UE 101 and the cellular network 102 at least hasthe possibility to arrange for successfully transmission on the lowerlayers employing the LTE frequency band 112.

Next, the uplink transmission 181 of the data packet 290 from the UE 101to the eNB 102 b via the LTE frequency band 112 at 208, 210 is discussedin detail. As will be appreciated from the above, the furthertransmission timeout monitored by the further transmission timeout timer280-2. If the checking yields that the receipt of the data packet 290 isnot acknowledged by the cellular network 102 and depending on saidmonitoring of the further transmission timeout, the UE 101 selectivelyre-sends the data packet 290 via the LTE frequency band 112; this is thecase at 210.

In the scenario of FIG. 2, the transmission timeout timer 280-1 and thefurther transmission timeout timer 280-2 are employed. Alternatively oradditionally to relying on the transmission timeout timers 280-1, 280-2,it is possible to implement one or more retransmission counters (notshown in FIG.2).

Generally, the transmission timeout timers 280-1, 280-2 and/or theretransmission counters can be seen to be part of a respective ARQscheme. Hence, in the scenario of FIG. 2, properties of a correspondingfirst ARQ scheme for protecting the uplink transmission 181 via theLAA-LTE frequency band 111 are set and further properties of acorresponding second ARQ scheme for protecting the uplink transmission182 via the LTE frequency band 112 are set. Such properties of the ARQschemes may be preset according to fixed rules; alternatively oradditionally, they could be configured by the cellular network 102 on aper-connection basis. For the latter, Radio Resource Control (RRC)control signalling according to the 3GPP LTE radio access technology maybe employed. Here it is noted that the RRC control signalling forsetting properties of the ARQ scheme protecting transmission via theLAA-LTE frequency band 111 may be handled via the LTE frequency band112.

Generally, it is possible that the monitoring of the transmissiontimeout for the uplink and/or downlink transmission 181, 182 via theLAA-LTE frequency band 111 and/or the monitoring of the transmissiontimeout of the uplink and/or downlink transmission 181, 182 via the LTEfrequency band 112 relies on a threshold comparison. In particular, itis possible that a threshold comparison is executed between apredetermined threshold and the transmission timeout timer 280-1,respectively the retransmission counter (not shown in FIG. 2). Thepredetermined threshold can be chosen such that it corresponds tosending the data packet 290 to the cellular network 102 in the LAA-LTEfrequency band 111 for a time duration which is shorter than a lifetimeindication of the data packet 290.

Likewise, it is possible that a further threshold comparison is executedbetween a further predetermined threshold and the further transmissiontimeout timer 280-2, respectively a further retransmission counter (notshown in FIG. 2). The further predetermined threshold can, again,correspond to the sending of the data packet 290 to the cellular network102 in the LTE frequency band 112 for a time duration which is shorterthan the lifetime indication of the data packet 290.

Depending on the implementation of the monitoring of the transmissiontimeout, the predetermined threshold and/or the further predeterminedthreshold may also be referred to as initialization value of thecorresponding transmission timeout timers, respectively retransmissioncounters.

In such scenarios as discussed above, it is possible that—in view of thepotentially limited lifetime of the data packet 290—transmissionattempts are distributed across the LAA-LTE frequency band 111 and theLTE frequency band 112. Thus, over the entire lifetime of the datapacket 290, transmission is attempted in both frequency bands 111, 112.This allows increasing the likelihood for successful transmission of thedata packet 290.

As mentioned above, the predetermined threshold and/or the furtherpredetermined threshold as properties of corresponding ARQ schemes maybe determined based on a control message received from the cellularnetwork 102, e.g., in the LTE frequency band 111; such a scenariocorresponds to large degrees of the decision logic for configuring themonitoring of the transmission timeout residing in the cellular network102. In this respect, it is possible that the operation of the UE 101 isat least partly remote controlled by the cellular network 102.Alternatively or additionally, it is possible that the predeterminedthreshold and/or the further predetermined threshold are determined by alifetime indication of the data packet 290. E.g., the lifetimeindication of the data packet 290 may be implicitly given according topre-configured quality of service (QoS) rules implemented by the UE 101.It is also possible that the lifetime indication of the data packet 290is received by the MAC layer from a higher layer.

In FIG. 3, a scenario is illustrated which is comparable to the scenarioof FIG. 2; however, while FIG. 2 relates to the protection of the uplinktransmission 181, FIG. 3 relates to the protection of the downlinktransmission 182 from the cellular network 102 to the UE 101.

At 301, the data packet 290 is received by the MAC layer of the eNB 102c and stored in a respective transmit buffer (not shown in FIG. 3). Thistriggers initialization of the transmission timeout timer 280-1. Thedata packet 290 is unsuccessfully transmitted to the UE 101 in theLAA-LTE frequency band 111 a number of times at 302, 304, 306. None ofdownlink transmissions 182 at 302, 304, 306 is positively acknowledged.It could be possible in various scenarios, that each one of the downlinktransmissions at 302, 304, 306 is negatively acknowledged (not shown inFIG. 3).

Then, monitoring of the transmission timeout yields that thetransmission timeout timer 280-1 has elapsed or expired and that by thenthe data packet 290 has not been positively acknowledged by the UE 101.Because of this, a fallback to the LTE frequency band 112 is executed.Here, the first downlink transmission 182 of the data packet 290 at 308is positively acknowledged 309 by the UE 101 and further retransmissionattempts are not required. In particular, the downlink transmission 182at 308 of the data packet 290 is positively acknowledged at 309 before amonitoring of the transmission timeout yields that a furthertransmission timeout timer 280-2 has elapsed or expired.

As can be seen, from a comparison of FIGS. 2 and 3, the techniquesrelied upon for protecting the uplink transmission 181 of the datapacket 290 are comparable to the techniques relied upon for protectingthe downlink transmission 182 of the data packet 290. E.g., while withrespect to FIG. 3, a scenario has been shown where the first ARQ schemeemployed to protect the downlink transmission 182 in the LAA-LTEfrequency band 111 does not rely on negative acknowledgements, similartechniques may also be applied with respect to the first ARQ schemewhich is employed to protect the uplink transmission 181 in the firstfrequency band 111 (cf. FIG. 2).

Further, while with respect to FIGS. 2 and 3, acknowledgement schemeswhich rely on individual acknowledgement of the data packet 290 havebeen primarily described, it is also possible to use implicitacknowledgement schemes and/or block acknowledgement schemes. Suchtechniques may rely on a more or less implicit acknowledgement of thereceipt of the data packet 290, e.g., by signalling a lower bound and/oran upper bound of a sender window and/or reception window and/or byacknowledging a plurality of data packets at one time.

In FIG. 4, yet a further scenario is illustrated. In FIG. 4, a controlmessage 401 sent via the LTE frequency band 112 is employed to controlproperties of the first ARQ scheme employed by the UE 101 to protect theuplink transmission 181 of the data packet in the LAA-LTE frequency band111. The control message 401 can be according to the RRC scheduling ofthe 3GPP LTE radio access technology. E.g., the control message 401 canspecify a value of the transmission timeout timer 280-1. Generally, itis possible that properties of the ARQ schemes employed at the UE 101and/or the cellular network 102 are at least partly remote controlled.While also the scenario of FIG. 4 relates to protecting the uplinktransmission 181 of the data packet 290 from the UE 101 to the cellularnetwork 102, similar techniques may be readily applied for protectingthe downlink transmission 182.

In the scenario of FIG. 4, the second uplink transmission 181 of thedata packet 290 from the UE 101 to the eNB 102 c in the LAA-LTEfrequency band 111 at 405 is successful; because of this, the seconduplink transmission 181 at 405 is positively acknowledged at 406.Because the transmission of the data packet 290 in the LAA-LTE frequencyband 111 has already been positively acknowledged at 406 before thetransmission timeout timer 280-1 expires, it is not necessary to executethe fallback to uplink transmission 181 of the data packet 290 via theLTE frequency band 112.

With respect to the scenario of FIG. 4, it is noted that the controlsignalling is handled via the LTE frequency band 112; i.e., the controlmessage 401 according to the RRC framework is sent in the LTE frequencyband 112, as well as the positive and negative acknowledgements at 404,406. In other words, the ARQ scheme employed by the UE 101 to protectthe uplink transmission 181 of the data packet 290 in the LAA-LTEfrequency band 111 relies at least partly on resources in the LTEfrequency band 112. Thus, while payload data transmission is handled bythe LAA-LTE frequency band 111, a high transmission reliability or thecontrol signalling can be achieved by relying on the LTE frequency band112.

In a case, as discussed with respect to FIG. 4 where at least parts ofthe properties of the first ARQ scheme employed by the UE 101 to protectthe uplink transmission 181 of the data packet 290 in the LAA-LTEfrequency band 111 are controlled by the cellular network 102, it ispossible that the cellular network 102 gets better control over thetotal traffic load on the LTE frequency band 112. This can be achievedby allowing the cellular network 102 specifying, e.g., the number ofadditional retransmission in the LTE frequency band 112 is zero;likewise, it is possible that a value of the further retransmissiontimer 280-2 (cf. FIG. 2) is set to zero. Likewise, it is possible that atimer value of the transmission timeout timer 280-1 for transmission inthe LAA-LTE frequency band 111 is set to zero. In such a scenario, it ispossible that the cellular network 102 fully controls the traffic loadon the LTE frequency band 111, lower layer transmission delay, andtransmission buffer requirements of the UE 101 in a dynamic manner. Inparticular, it is possible that the respective control logic of thecellular network 102 considers a current interference situation in theLAA-LTE frequency band 111; the current interference situation may havea significant impact on a transmission reliability for transmissions181, 182 in the LAA-LTE frequency band 111. Here, the cellular network102 may autonomously determine the interference situation and/or rely onrespective indications received from the UE 101 via at least one of theLAA-LTE frequency band 111 and the LTE frequency band 112.

Generally, in such scenarios where the logic for setting properties ofthe ARQ scheme implemented to protect transmission via the LAA-LTEfrequency band 111 resides at least partly in the cellular network 102,it is possible that a control message indicating correspondingproperties of said ARQ scheme is sent via the LTE frequency band 112.The ARQ properties may include the predetermined threshold forcomparison with the transmission timeout time 280-1 and/or acorresponding retransmission counter. The ARQ properties may bedetermined based on the interference situation, respectively the trafficload in the LAA-LTE frequency band 111. Alternatively or additionally,the properties may be determined based on a quality report of the UE101. The quality report may indicate such properties as the ChannelQuality Report (CQI), a packet error rate, a bit error rate, aretransmission statistic of retransmission attempts of the UE 101, etc.Such information may be referred to as interference awareness reporting;such information may be directly or indirectly indicative of theinterference situation in the LAA-LTE frequency band 111.

The quality report may be sent from the UE 101 to the cellular network102 in the LTE frequency band 112.

Above, scenarios have been discussed where the decision logic forcertain properties of the ARQ scheme implemented to protect the uplinktransmission 181 and/or the downlink transmission 182 via the LAA-LTEfrequency band 111 resides at least partly in the cellular network 102.Likewise, it is possible that scenarios are implemented where therespective decision logic resides at least partly at the UE 101. Then,the respective control message for remote control may be sent by the UE101 to the cellular network 102 in the LTE frequency band 112.

In FIG. 5, the first ARQ scheme 501 and the second ARQ scheme 502 areshown. In the scenario of FIG. 5, Hybrid ARQ (HARQ) schemes 501, 502 areemployed which rely on, both, FEC, as well as retransmission controlledby the ARQ scheme. The first HARQ scheme 501 is for protecting theuplink and/or downlink transmission 181, 182 via the LAA-LTE frequencyband 111; respectively, the second ARQ 502 is employed to protect uplinkand/or downlink transmission 181, 182 via the LTE frequency band 112.

As can be seen from FIG. 5, the first ARQ scheme 501 differs from thesecond ARQ scheme 502 in that at least some of their properties differfrom each other. E.g., the number of retransmission attempts, i.e., apredefined threshold or timer initialization value to be compared with aretransmission counter, equals four in the scenario of the first ARQscheme 501—while it equals infinity in the scenario of the second ARQscheme 502. Further properties of the ARQ schemes 501, 502 which areillustrated in FIG. 5 are: a predefined threshold to be compared with atransmission timeout timer 280-1, 280-2; a flag indicating the use ofnegative acknowledgements; a flag indicating the use of positiveacknowledgements; a flag indicating the use of block acknowledgements;and a size of a FEC checksum.

In particular, in the case where uplink transmission 181 from the UE 101to the cellular network 102 is protected employing the ARQ schemes 501,502, it is possible that all or some of these properties of the ARQschemes 501, 502 are set by the cellular network 102. E.g., it ispossible that at least one property of the first ARQ scheme 501 isdetermined based on at least one of the interference situation in theLAA-LTE frequency band 111 and the quality report received from the UE101. E.g, the UE 101 can be configured to send the quality report viathe wireless interface in the LTE frequency band 112. The quality reportcan specify such parameters as the CQI, the packet error rate, the biterror rate, retransmission statistics, etc. Generally, the qualityreport can be indicative of an interference awareness of the UE 101 fortransmission in the first frequency band 101. Then, the cellular network102 can be configured to send a respective control message to the UE 101in the second frequency band 112. The control message indicating therespective property of the first ARQ scheme 501.

In FIG. 6, the data packet 290 is illustrated at greater detail. Thedata packet 290 comprises a header and a payload portion (not shown inFIG. 6). In the header, various properties of the data packet 290 can bespecified. In particular, it is possible that a QoS parameter isassociated with the data packet 290; the QoS parameter can at leastimplicitly specify the lifetime of the data packet 290. E.g., saidassociation of the QoS parameter may be achieved by transmitting thedata packet 290 via a specific bearer. Each bearer may be assigned acertain QoS parameter. E.g., streaming movie would be assigned aspecific QoS parameter which may be different than, e.g., voice overInternet Protocol (VoIP). As the data packet 290 is associated with aspecific bearer, the data packet 290 is implicitly associated with thecorresponding QoS parameter. Further, a content indicator is included inthe header portion of the data packet 290. Also from the contentindication it is possible to conclude on the lifetime of the data packet290.

FIG. 7 is schematic illustration of the UE 101. The UE 101 comprises aprocessor 101-2. E.g., the processor 101-2 can be a multi-coreprocessor; alternatively or additionally, it is possible to rely ondistributed computing.

Further, the UE 101 comprises a memory 101-3. E.g., the memory can be avolatile or non-volatile memory. Control data is stored in the memory101-3. When the control data is executed by the processor 101-2,techniques according to various embodiments as explained above inconnection with protecting uplink transmission 181 and/or downlinktransmission 182 are executed. In particular, the processor 101-2, whenexecuting the control data received from the memory 101-3, can beconfigured to send the data packet 290 to the cellular network 102 viathe wireless interface 101-1 in the LAA-LTE frequency band 111 and/or inthe LTE frequency band 112; further, the processor 101-2 can beconfigured to check if receipt of the data packet 290 is acknowledged bythe cellular network 102. Further, the processor 101-2 can be configuredto employ the first ARQ scheme 101 and/or the second ARQ scheme 502;further, the processor 101-2 can be configured to monitor thetransmission timeout by executing a threshold comparison between thetransmission timeout timers 280-1, 280-2 and a respective predefinedthreshold.

As can be seen from FIG. 7, the wireless interface 101-1 of the UE 101comprises a first transmitter 101-la and a first receiver 101-1 b fortransceiving in the LAA-LTE frequency band 111; further, the wirelessinterface 101-1 comprises a second transmitter 101-1 c and a secondreceiver 101-1 d for transceiving in the LTE frequency band 112.Depending on the particular choice of the LAA-LTE frequency band 111 andthe LTE frequency band 112, it is also possible that the wirelessinterface 101-1 only comprises a single transceiver which is configuredto communicate in, both, the LAA-LTE frequency band 111 and the LTEfrequency band 112 (a scenario not shown in FIG. 7).

The UE 101 further comprises a human machine interface (HMI) 101-4. Itis possible to receive user instructions from a user via the HMI 101-4.Further it is possible to output information to the user via the HMI101-4. The HMI 101-4 may comprise a touchpad, a mouse, a keyboard, avoice recognition unit, one or more control lights, a display, and/orone or more buttons, etc.

In FIG. 8, the eNBs 102 b, 102 c are illustrated at greater detail. TheeNBs 102 b, 102 c comprise a processor 102 b-2, e.g., the processor 102b-2 can be a multi-core processor and/or rely on shared computing.

Further, the eNBs 102 b, 102 c comprise a memory 102 b-3. The memory 102b-3 can be a volatile or a non-volatile memory. The memory 102 b-3comprises control data which, when executed by the processor 102 b-2,causes the processor 102 b-2 to execute techniques according to variousembodiments as explained above. In particular, when the processor 102b-2 executes the control data received from the memory 102 b-3, theprocessor 102 b-2 can execute techniques as explained above relating tothe protection of uplink transmission 181 and/or downlink transmission182. In particular, the processor 102 b-2, when executing the controldata received from the memory 102 b-3, can be configured to send thedata packet 290 to the communication device 101 via the wirelessinterface 102 b-1 in the LAA-LTE frequency band 111 and/or in the LTEfrequency band 112; further, the processor 102 b-2 can be configured tocheck if receipt of the data packet 290 is acknowledged.

Further, the processor 102 b-2 can be configured to employ the first ARQscheme 101 and/or the second ARQ scheme 502; further, the processor 102b-2 can be configured to monitor the transmission timeout by executing athreshold comparison between the transmission timeout timers 280-1,280-2 and a respective predefined threshold.

The eNBs 102 b, 102 c comprise a wireless interface 102 b-1. Thewireless interface 102 b-1 comprises a transmitter 102 b-1 a and areceiver 102 b-1 b. The wireless interface 102 b-1 is configured tocommunicate with the UE 101 in the LAA-LTE frequency band 111 in thecase of the eNB 102 c and/or the LTE frequency band 112 in the case ofthe eNB 102 b. E.g., in a case where the functionality of both eNBs 102b, 102 c is co-located in a single entity, it is possible that therespective interface 102 b-1 comprises two transmitters and tworeceivers (not shown in FIG. 8) which are respectively configured tocommunicate in a different one of the two frequency bands 111, 112.

Further, the eNBs 102 b, 102 c comprising HMI 102 b-4. It is possible toreceive a user input via the HMI 102 b-4 and/or to output information tothe user via the HMI 102 b-4.

The HMI 102 b-4 may comprise a touchpad, a mouse, a keyboard, a voicerecognition unit, one or more control lights, a display, and/or one ormore buttons, etc.

Summarizing, above techniques have been describe where retransmissionsof a data packet are handled primarily by a first ARQ scheme via theLAA-LTE frequency band; as a fallback, retransmission of the data packetare handled by a second ARQ scheme via the LTE frequency band. In asituation where the interference level in the LAA-LTE frequency band iscomparably low, a simple and effective transmission protection can beemployed; successful reception of the data packet may be achieved at acomparably low latency. Also in scenarios where the interference levelin the LAA-LTE frequency band is comparably high, the overalltransmission reliability may not be significantly degraded without theneed of higher layer retransmissions—while, nonetheless, most trafficmay be handled by the LAA-LTE frequency band. According to thetechniques, the fallback is configurable; the respective control logicmay reside at the cellular network and/or the UE. In order to implementthe control of the fallback, control signalling may be executed; thecontrol signalling may reside in the LTE frequency band, even if thepayload traffic is handled in the LAA-LTE frequency band. Triggercriteria for triggering the fallback may be expiry of a transmissiontimeout timer and/or a retransmission counter; respective thresholds maybe configured by the cellular network. The thresholds may be determinedbased on a lifetime of the data packet and/or the interference level ofthe LAA-LTE frequency band and/or a quality report provided by the UE.

Although the invention has been shown and described with respect tocertain preferred embodiments, equivalents and modifications will occurto others skilled in the art upon the reading and understanding of thespecification. The present invention includes all such equivalents andmodifications, and is limited only by the scope of the following claims.

1. A communication device, the communication device comprising: awireless interface configured to communicate with a cellular network ina first frequency band and to communicate with the cellular network in asecond frequency band, the second frequency band being at least partlydifferent from the first frequency band, at least one processorconfigured to send a data packet to the cellular network via thewireless interface in the first frequency band, wherein the at least oneprocessor is further configured to check if receipt of the data packetis acknowledged by the cellular network, wherein the at least oneprocessor is further configured to selectively send the data packet tothe cellular network via the wireless interface in the second frequencyband depending on said checking.
 2. The communication device of claim 1,wherein the at least one processor is configured to send the data packetto the cellular network via the wireless interface in the firstfrequency band employing a first automatic repeat request scheme,wherein the at least one processor is further configured to selectivelysend the data packet to the cellular network via the wireless interfacein the second frequency band employing a second automatic repeat requestscheme.
 3. The communication device of claim 1, wherein the at least oneprocessor is configured to, as part of said sending of the data packetto the cellular network via the wireless interface in the firstfrequency band, monitor a transmission timeout of the data packet and,if said checking yields that the receipt of the data packet is notacknowledged by the cellular network and depending on said monitoring ofthe transmission timeout, to selectively re-send the data packet via thewireless interface to the cellular network in the first frequency band.4. The communication device of claim 3, wherein the at least oneprocessor is configured to selectively execute said sending of the datapacket to the cellular network via the wireless interface in the secondfrequency band if the monitoring of the transmission timeout yields anelapsed transmission timeout of the data packet.
 5. The communicationdevice of claim 3, wherein the at least one processor is configured tomonitor the transmission timeout of the data packet by executing athreshold comparison between a predetermined threshold and at least oneof a transmission timeout timer and a retransmission counter, whereinthe predetermined threshold corresponds to sending of the data packet tothe cellular network in the first frequency band for a time durationwhich is shorter than a lifetime indication of the data packet.
 6. Thecommunication device of claim 5, wherein the at least one processor isconfigured to, as part of said sending of the data packet to thecellular network via the wireless interface in the second frequencyband: monitor a further transmission timeout of the data packet; if saidchecking yields that the receipt of the data packet is not acknowledgedby the cellular network and depending on said monitoring of the furthertransmission timeout, selectively re-send the data packet via thewireless interface to the cellular network in the second frequency band,wherein the at least one processor is configured to monitor the furthertransmission timeout of the data packet by executing a further thresholdcomparison between a further predetermined threshold and at least one ofa further transmission timeout timer and a further retransmissioncounter, wherein the further predetermined threshold corresponds tosending of the data packet to the cellular network in the secondfrequency band for a time duration which is shorter than the lifetimeindication of the data packet.
 7. The communication device of claim 5,wherein the at least one processor is configured to determine at leastone of the predetermined threshold and the further predeterminedthreshold based on at least one of a control message received via thewireless interface from the cellular network in the second frequencyband and the lifetime indication of the data packet.
 8. Thecommunication device of claim 1, wherein the first frequency band is anunlicensed frequency band, wherein the wireless interface is configuredto transceive according to an Licensed Assisted Access LTE datatransmission procedure in the first frequency band, wherein the secondfrequency band is a licensed frequency band, wherein the wirelessinterface is configured to transceive according an LTE-licensed datatransmission procedure in the second frequency band.
 9. Thecommunication device of claim 1, wherein the communication device is amobile device of a group comprising a mobile phone, a smartphone,tablet, a personal digital assistant, a mobile music player, a smartwatch, a wearable electronic equipment, and a mobile computer.
 10. Amethod, the method comprising: at least one processor of a communicationdevice sending a data packet to a cellular network via a wirelessinterface of the communication device in a first frequency band, the atleast one processor checking if receipt of the data packet isacknowledged by the cellular network, depending on said checking, the atleast one processor selectively sending the data packet to the cellularnetwork via the wireless interface in a second frequency band, thesecond frequency band being at least partly different from the firstfrequency band.
 11. The method of claim 10, wherein the method isexecuted by a communication device of claim
 1. 12. A node of a cellularnetwork, the node comprising: a wireless interface configured tocommunicate with a communication device connected to the cellularnetwork in a first frequency band and to communicate with thecommunication device in a second frequency band, the second frequencyband being at least partly different from the first frequency band, atleast one processor configured to send a data packet to thecommunication device via the wireless interface in the first frequencyband, wherein the at least one processor is further configured to checkif receipt of the data packet is acknowledged by the communicationdevice, wherein the at least one processor is further configured toselectively send the data packet to the communication device via thewireless interface in the second frequency band depending on saidchecking.
 13. The node of claim 12, wherein the at least one processoris configured to send the data packet to the communication device viathe wireless interface in the first frequency band employing a firstautomatic repeat request scheme, wherein the at least one processor isfurther configured to selectively send the data packet to thecommunication device via the wireless interface in the second frequencyband employing a second automatic repeat request scheme.
 14. The node ofclaim 13, wherein the at least one processor is configured to determinea property of the first automatic repeat request scheme based on atleast one of an interference situation in the first frequency band and aquality report received from the communication device.
 15. The node ofclaim 12, wherein the at least one processor is configured to, as partof said sending of the data packet to the communication device via thewireless interface in the first frequency band: monitor a transmissiontimeout of the data packet; and if said checking yields that the receiptof the data packet is not acknowledged by the communication device anddepending on said monitoring of the transmission timeout, selectivelyre-send the data packet via the wireless interface to the communicationdevice in the first frequency band.
 16. The node of claim 15, whereinthe at least one processor is configured to selectively execute saidsending of the data packet to the communication device via the wirelessinterface in the second frequency band if the monitoring of thetransmission timeout yields an elapsed transmission timeout of the datapacket.
 17. The node of claim 15, wherein the at least one processor isconfigured to monitor the transmission timeout of the data packet byexecuting a threshold comparison between a predetermined threshold andat least one of a transmission timeout timer and a retransmissioncounter, wherein the predetermined threshold corresponds to sending ofthe data packet to the communication device in the first frequency bandfor a time duration which is shorter than a lifetime indication of thedata packet.
 18. The node of claim 17, wherein the at least oneprocessor is configured to, as part of said sending of the data packetto the communication device via the wireless interface in the secondfrequency band: monitor a further transmission timeout of the datapacket; if said checking yields that the receipt of the data packet isnot acknowledged by the communication device and depending on saidmonitoring of the further transmission timeout, selectively re-send thedata packet via the wireless interface to the communication in thesecond frequency band, wherein the at least one processor is configuredto monitor the further transmission timeout of the data packet byexecuting a further threshold comparison between a further predeterminedthreshold and at least one of a further transmission timeout timer and afurther retransmission counter, wherein the further predeterminedthreshold corresponds to sending of the data packet to the communicationdevice in the second frequency band for a time duration which is shorterthan the lifetime indication of the data packet.
 19. The node of claim17, wherein the at least one processor is configured to determine atleast one of the predetermined threshold and the further predeterminedthreshold based on at least one of a interference situation oftransmission in the first frequency band and the lifetime indication ofthe data packet, wherein the at least one processor is furtherconfigured to send a control message indicating at least one of thepredetermined threshold and the further predetermined threshold via thewireless interface to the communication device in the second frequencyband.
 20. The node of claim 12, wherein the first frequency band is anunlicensed frequency band, wherein the wireless interface is configuredto transceive according to an License Assisted Access data transmissionprocedure in the first frequency band, wherein the second frequency bandis a licensed frequency band, wherein the wireless interface isconfigured to transceive according an LTE-licensed data transmissionprocedure in the second frequency band.
 21. A method, the methodcomprising: at least one processor of a node of a cellular networksending a data packet to a communication device connected to thecellular network via a wireless interface of the node in a firstfrequency band, the at least one processor checking if receipt of thedata packet is acknowledged by the communication device, depending onsaid checking, the at least one processor selectively sending the datapacket to the communication device via the wireless interface in asecond frequency band, the second frequency band being at least partlydifferent from the first frequency band.
 22. A node of a cellularnetwork, the node comprising: a wireless interface configured tocommunicate with a communication device connected to the cellularnetwork in a first frequency band and to communicate with thecommunication device in a second frequency band, the second frequencyband being at least partly different from the first frequency band, atleast one processor configured to receive a data packet from thecommunication device via the wireless interface in the first frequencyband, wherein the at least one processor is further configured to checkif receipt of the data packet is successful, wherein the at least oneprocessor is further configured to selectively receive the data packetfrom the communication device via the wireless interface in the secondfrequency band depending on said checking.
 23. The node of claim 22,wherein the at least one processor is configured to receive the datapacket to the communication device via the wireless interface in thefirst frequency band employing a first automatic repeat request scheme,wherein the at least one processor is further configured to selectivelyreceive the data packet to the communication device via the wirelessinterface in the second frequency band employing a second automaticrepeat request scheme.
 24. The node of claim 23, wherein the at leastone processor is configured to determine a property of the firstautomatic repeat request scheme based on at least one of an interferencesituation in the first frequency band and a quality report received fromthe communication device, wherein the at least one processor isconfigured to send a control message to the communication device via thewireless interface in at least one of the first frequency band and thesecond frequency band, the control message indicating the determinedproperty of the first automatic repeat request scheme.
 25. The node ofclaim 22, wherein the at least one processor is configured to send atleast one of a positive acknowledgement and a negative acknowledgementof receipt of the data packet, depending on said checking.